若 $\lim _{x \rightarrow x_0} f(x)=\infty, \lim _{x \rightarrow x_0} g(x)=\infty$, 则
$\text{A.}$ $\lim _{x \rightarrow x_0}[f(x)+g(x)]=\infty$.
$\text{B.}$ $\lim _{x \rightarrow x_0}[f(x)-g(x)]=\infty$.
$\text{C.}$ $\lim _{x \rightarrow x_0} f(x) g(x)=\infty$.
$\text{D.}$ $\lim _{x \rightarrow x_0} \frac{f(x)}{g(x)}=\infty$.